As far as I know the radar still can't see stopped objects by itself. So unless it has some additional data from the camera it can completely miss the bus. That isn't surprising if the sun is in the way. Now if the bus was indeed moving and the radar should have locked onto it then indeed there is something messed up. In any case you should email the autopilot team. I'm really hoping people aren't reporting here, and not emailing tesla as well. Just copy and paste it.